[Ovmsdev] GPS theft alert

[Michael Balzer]

Craig,

nice analysis & solution, merged.

Using the config macro would have been OK though, we will need to 
introduce separate builds for revision 3 anyway to benefit from the 
fixed SPIRAM issue.

Btw: did you find some time to do the performance tests I suggested? 
Doesn't take long, just a couple of minutes.

Regards,
Michael


Am 10.03.21 um 05:47 schrieb Craig Leres:
> This issue will be solved with this pull request:
>
>
> https://github.com/openvehicles/Open-Vehicle-Monitoring-System-3/pull/585
>
> Starting with revision 2 of the ESP32, the function of the "enable 
> wakeup interrupt" bit in the interrupt enable register changed to mean 
> "divide BRP by 2". The OVMS SJA1000 code enables "all interrupts 
> except arbitration loss" which includes the wakeup interrupt/divide 
> BRP bit. This causes the can baud to be configured at half the 
> requested speed; a workaround is to set the speed to 2X desired.
>
> The (minimal) fix is to clear this bit when revision is >= 2. Since 
> we're not using sleep, we could also just always clear that bit. But 
> in the long run I'm hopeful that the ability to use effectively larger 
> BRP values will mean V3 hardware will be able to run can1 at lower 
> speeds, e.g. 33K.
>
> At first I was looking at the can module in the esp-idf; even the old 
> version we're running has code to do with this issue! But cleverly, 
> it's a compile time #ifdef instead of run time check based on observed 
> version (?!?!) I think the way it works is you define 
> CONFIG_ESP32_REV_MIN to the lowest hardware version you want to 
> support and it assumes you have at least that. Which seems silly to 
> me. I tried converting it to a run time check and it didn't work -- 
> that's when I figured out OVMS uses it's own SAJ1000 driver code.
>
> Thanks to Thomas Heuer for reaching out to me and giving a pointer to 
> this forum post:
>
>     https://www.esp32.com/viewtopic.php?t=15581#p59670
>
> which was key in figuring this out.
>
>         Craig

-- 
Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
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